For all the concern about how we’ll feed a projected 9 billion people by 2050, there’s little talk about where everyone will go to the loo. How we'll move all that waste away from where people live -- plumbing -- is just one issue. With some 2.6 billion people, or 40 percent of the world’s population, already lacking adequate drinking water, building the right sanitation infrastructure today is a foundation for public health and economic development for decades to come.

Rose George has probed these issues for years, most notably in her 2008 book The Big Necessity: The Unmentionable World of Human Waste and Why it Matters, a look at toilets, sewers and water around the world. We spoke last month about the world’s dwindling supply of fresh water and its ever-increasing volumes of sewage.

Q: This isn’t the easiest topic to bring up in polite company. How does common avoidance of this topic interfere with solving problems?A: If you work in sanitation you have to pay attention to psychology. People are quirky and irrational and perverse. In some areas, treated wastewater is pumped into a local aquifer, before it’s withdrawn as clean, “natural” fresh water. It’s just a sleight of hand. The water is perfectly clean when it leaves the sewage treatment plant. It’s actually dirtier once you pump it out of the aquifer or a river.

Q: Even though we know intellectually that it’s fine, many people just don’t want to hear about clean, healthy drinking water that’s been through the sewage system. It’s the idea of it.A: It’s what we call the toilet-to-tap "ick" factor. NASA astronauts have been drinking recycled urine for ages. If you’re drawing from any single major lake in the U.S., you are already drinking someone else's discharge. I'm probably a bit too blunt about it.

Q: But bluntness probably helps sometimes, too, I imagine.
A: If you disgust people enough, they immediately change their behavior and rush off and build latrines. You can encourage change with prize-giving or in developing countries make it a competition with a neighboring village. The Bill and Melinda Gates Foundation has started a program in India to encourage brides to insist their husbands build them a toilet before they agree to marriage, it’s called “No Loo, No I Do.”

Q: How bad is the problem in the U.S?A: Some reports say nearly 2 million Americans live without proper plumbing or sanitation.

Q: Biologists tell us that in nature there’s no such thing as waste. Everything just becomes something else. That sure doesn’t seem like it’s the case in cities.
A: A really astonishing fact is the absolute scorn for seeing sewage as a resource. Only about 500 of the 16,000 wastewater treatment plants in the U.S. do anything with the waste they pull from the water. Marco Polo saw bio-methane being used in China. One hundred and fifty years ago we had streetlamps powered from sewer gas. Most sewage plants just flame off the methane. In England Thames Water says it's saving 15 million pounds a year [almost $20 million] on electric bills because they use the methane.

Q: How do you upgrade, in short order, the 2.6 billion people without proper sanitation? Or can you?
A: I’ve spoken to big companies and they say people are too poor. That’s a gross misunderstanding. People will buy something if they see its value – and that includes toilets. In fact, the big buzz in the sanitation world for the toilet-less is sanitation marketing. We’ve learned over the years that you can’t just give someone a toilet. You have to make it a consumer product, like the Japanese did.

Q: Are toilets the answer everywhere?
A: Before, the idea was that everyone has to aspire to a flush toilet and sewer system, but that’s inappropriate for any country with a shortage of water. The answer now is whatever works.

Q: Is this a wholly systemic problem, or are there things consumers could make an impact with?
A: The most important thing we can do is stop discarding waste in water, and start thinking of it as a resource. Ideally we'd all have self-contained composting toilets in our apartments, but that's not going to happen. It could be simple things like not flushing as much. If everybody flushed a few times a day less that could have a real impact. And we must look at the costs beyond money. New York City is discharging raw sewage into its waters every time it rains, so that has an environmental cost. [New York's fateful 19th-century decision to build a single set of pipes to carry away sewage and storm water has left today's sewage treatment plants unable to cope with the flow when heavy rains hit -- P.G.]

Q: How do you get all the players -- the consumer, the state, utilities -- to pay attention to the sewage crisis?
A: Sewage ought to get attention simply from the day-to-day deaths from diarrhea in the developing world -- preventable deaths. It is completely ignored. Basic, boring diarrhea doesn’t get any attention. There's still a lot of squeamishness and there needs to be a bit more courage to talk about it.

Q: What are you doing now?
A: Working on book about merchant shipping and the sea. I went pirate-hunting. I was on a container ship for six weeks.

Q: What the most memorable book you've read lately?
A: The Urban Whale, by Scott D. Kraus and Rosalind M. Rolland. It's about the North Atlantic Right whale, New York's local whale, about how industry is having an impact on the ocean and its wildlife. It's enlightening.